Surgical stapling device with releasable knife carrier

ABSTRACT

A surgical stapling device includes reload assembly that is supported on a distal portion of an elongate shaft of the surgical stapling device. The reload includes a housing, a pusher assembly movably supported within the housing, a knife carrier movably supported within the pusher assembly, and an annular knife supported on the knife carrier. The elongate body includes a pusher drive member and a knife carrier pusher. The knife carrier includes first engagement structure that is configured to releasably engage second engagement structure formed on the knife carrier pusher to releasably couple the knife carrier pusher to the knife carrier. The knife carrier supports at least one detent that is movable into contact with a distal portion of the pusher drive member as the knife carrier is retracted to urge the first engagement structure out of engagement with the second engagement structure to uncouple the knife carrier from the knife carrier pusher.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation application which claims the benefit of and priority to U.S. patent application Ser. No. 15/467,153, filed on Mar. 23, 2017, the entire content of which is incorporated herein by reference.

BACKGROUND 1. Technical Description

The present disclosure is directed to surgical stapling devices and, more particularly, to surgical stapling devices that include a knife carrier that is releasably coupled to a knife carrier pusher.

2. Background of Related Art

Conventional circular stapling devices include an elongate body and a shell or reload assembly supported on a distal portion of the elongate body. The reload assembly includes a staple cartridge that supports a plurality of staples, a pusher that is movable in relation to the staple cartridge to eject staples from the staple cartridge, a knife, and a knife carrier that supports the knife and is movable through the staple cartridge to core tissue. The surgical stapling device also includes a pusher drive member and a knife carrier pusher that are supported within the elongate body. The pusher drive member is engaged with the staple pusher and is movable to move the staple pusher to eject staples from the staple cartridge. Similarly, the knife carrier pusher is engaged with the knife carrier and is movable to effect movement of the knife carrier to core tissue. In some circular stapling devices, the knife carrier pusher and the knife carrier are separable to facilitate separation of the reload assembly from the elongate body of the surgical stapling device.

In some designs, a back angle may be formed on the knife carrier pusher to facilitate separation of the knife carrier pusher from the knife carrier. In these designs, if the back angle selected is too small, the knife carrier can be damaged upon removal of the reload from the elongate body, and if the back angle selected is too large, disengagement of the knife carrier pusher from the knife carrier can occur prematurely such that full retraction of the knife is not achieved.

A need exists in the stapling arts for a simple but reliable mechanism to effect engagement and disengagement of the knife carrier and the knife carrier pusher at the appropriate times.

SUMMARY

In one aspect of the disclosure, a surgical stapling device includes an elongate body defining a longitudinal axis and having a proximal portion and a distal portion, and a reload assembly. The elongate body includes a pusher drive member and a knife carrier pusher. The pusher drive member has an inner surface defining a through bore having a tapered distal portion. The reload assembly includes a housing, a staple cartridge supporting a plurality of staples, and a pusher assembly movably supported within the housing between a retracted position and an advanced position to eject the plurality of staples from the staple cartridge. The pusher assembly has an inner surface defining a through bore. The inner surface has a proximal portion defining a counter bore. The reload assembly also includes a knife carrier supporting a knife. The knife carrier includes first engagement structure and at least one detent. The knife carrier pusher includes second engagement structure configured to releasably engage the first engagement structure of the knife carrier to couple the knife carrier pusher to the knife carrier. The first engagement structure is movable from a first position engaged with the second engagement structure to a second position disengaged from the second engagement structure. When the stapling device is in a pre-fired state, the at least one detent is positioned within the counter bore of the pusher assembly, and when the knife carrier is retracted after the stapling device has been actuated to eject the plurality of staples and to cut tissue, the detents are positioned to engage the tapered distal portion of the pusher drive member to urge the first engagement structure from the first position towards the second position to uncouple the knife carrier from the knife carrier pusher.

In embodiments, the knife carrier includes a proximal portion defined by a plurality of flexible legs.

In some embodiments, the at least one detent includes a detent supported on each of the plurality of flexible legs.

In certain embodiments, each of the detents extends outwardly from a longitudinal axis of the knife carrier.

In embodiments, the knife carrier is movably positioned within the through bore defined by the pusher assembly.

In some embodiments, each of the detents is integrally formed with a respective one of the plurality of flexible legs.

In certain embodiments, the first engagement structure is formed on the proximal portion of the plurality of flexible legs.

In embodiments, the first engagement structure includes a recess formed on the proximal portion of the plurality of flexible legs.

In some embodiments, the recess includes an annular channel.

In certain embodiments, the proximal portion of each of the plurality of flexible legs is tapered towards a longitudinal axis of the knife carrier in the proximal direction.

In embodiments, the second engagement structure includes a protrusion configured to be received within the recess of the first engagement structure.

In some embodiments, the protrusion is annular.

In certain embodiments, the recess of the first engagement structure is defined by a proximal wall that is orthogonal in relation to the longitudinal axis of the knife carrier.

In embodiments, the protrusion of the second engagement structure is defined by a proximal wall which is orthogonal in relation to the longitudinal axis of the knife carrier pusher.

In some embodiments, the proximal wall of the second engagement structure is positioned to engage the proximal wall of the first engagement structure to translate proximal movement of the knife carrier pusher into proximal movement of the knife carrier.

In certain embodiments, the handle assembly is an electrically powered handle assembly.

In embodiments, the reload assembly is releasably coupled to the elongate body.

In some embodiments, the pusher assembly includes an annular pusher and a staple pushing member.

In certain embodiments, the annular pusher is positioned to abut a proximal portion of the staple pushing member.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the presently disclosed surgical stapling device including a releasable knife carrier are described herein below with reference to the drawings, wherein:

FIG. 1 is a side perspective view of one exemplary embodiment of the presently disclosed surgical stapling device including a reload assembly and an anvil assembly with the anvil assembly in an approximated position;

FIG. 2 is an enlarged view of the indicated area of detail shown in FIG. 1;

FIG. 3 is a side perspective view with parts separated of a distal portion of presently disclosed stapling device including the reload assembly and anvil assembly shown in FIG. 2;

FIG. 4 is a side perspective view from a proximal end of an annular pusher of a pusher assembly of the reload assembly shown in FIG. 3;

FIG. 4A is a side perspective view from a proximal portion of a knife carrier of the reload assembly shown in FIG. 3;

FIG. 5 is a side perspective view from a distal portion of a knife carrier pusher of the distal portion of the stapling device shown in FIG. 3;

FIG. 5A is a side perspective view of a pusher drive member of the distal portion of the stapling device shown in FIG. 3;

FIG. 6 is a cross-sectional view taken along section line 6-6 of FIG. 2 illustrating the distal portion of the surgical stapling device in a pre-fired state;

FIG. 6A is an enlarged view of the indicated area of detail shown in FIG. 6;

FIG. 6B is a side cross-sectional view of the distal portion of the surgical stapling device shown in FIG. 6 in a post-fired state with the knife carrier and knife carrier pusher in a retracted position;

FIG. 7 is a side cross-sectional view of the distal portion of the surgical stapling device shown in FIG. 6A in a post-fired state with the knife carrier and knife carrier pusher in an advanced position; and

FIG. 8 is a side cross-sectional view of the distal portion of the surgical stapling device shown in FIG. 7 in a post-fired state with the knife carrier and the drive member in retracted positions, and the knife carrier pusher moving towards its retracted position to facilitate separation of the knife carrier and the knife carrier pusher.

DETAILED DESCRIPTION OF EMBODIMENTS

The presently disclosed circular stapling device will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. In this description, the term “proximal” is used generally to refer to that portion of the stapling device that is closer to a clinician, while the term “distal” is used generally to refer to that portion of the stapling device that is farther from the clinician.

The presently disclosed circular stapling device includes a shell or reload assembly that is supported on a distal portion of an elongate shaft of the stapling device. The reload assembly includes a housing, a staple cartridge that supports a plurality of annular rows of staples, a staple pusher assembly, a knife carrier, and an annular knife supported on the knife carrier. The pusher assembly includes an inner surface defining a through bore. The inner surface of the pusher assembly has a proximal portion that defines a counter bore. The knife carrier is movably positioned within the through bore of the pusher assembly.

The elongate body includes a pusher drive member and a knife carrier pusher. The pusher drive member has an inner surface that defines a through bore that is aligned with the through bore of the pusher assembly. A distal portion of the inner surface of the pusher drive member is tapered outwardly in a distal direction. The knife carrier is movably positioned within the pusher assembly and pusher drive member and includes a plurality of proximally extending resilient legs that are movable from a first position engaged with the knife carrier pusher to couple the knife carrier with the knife carrier pusher to a second position disengaged from the knife carrier pusher. Each of the resilient legs supports an outwardly extending detent that is positioned within the counter bore of the pusher assembly when the stapling device is in a pre-fired state. When the stapling device is actuated to fire staples, the pusher drive member is advanced to advance the pusher assembly to eject staples from the staple cartridge. Thereafter, the knife carrier pusher is advanced to advance the knife carrier and the knife to cut or core tissue. After tissue is stapled and cored, the pusher drive member is retracted, and the knife carrier pusher is subsequently retracted to retract the knife carrier and the knife into the housing. As the knife carrier is retracted, the detents on the resilient legs of the knife carrier are moved from a position within the counter bore of the pusher assembly into contact with the tapered distal portion of the pusher drive member to urge the resilient legs of the knife carrier to the second position to uncouple the knife carrier pusher from the knife carrier. The presently disclosed reload assembly minimizes the likelihood of premature disengagement of the knife carrier from the knife carrier pusher while reducing the force required to effect uncoupling of the knife carrier from the knife carrier pusher after the knife has been fully retracted into the housing.

FIGS. 1 and 2 illustrate an exemplary embodiment of the presently disclosed surgical stapling device 10. The surgical stapling device 10 includes a handle assembly 12, an elongate body or adaptor assembly 14, a reload assembly 16, and an anvil assembly 18 supported for movement in relation to the reload assembly 16 between spaced and approximated positions as is known in the art. The reload assembly 16 includes a proximal portion 16 a that is releasably coupled to a distal portion 14 a of the elongate body 14. The handle assembly 12 includes a stationary grip 22, and actuation buttons 24 for controlling operation of the various functions of the surgical stapling device 10 including approximation of the reload and anvil assemblies 16, 18, firing of staples 36 from the reload 16, and cutting or coring of tissue. Although the surgical stapling device 10 is illustrated as an electrically powered stapling device including an electrically powered handle assembly 12 and an elongate body 14 in the form of an adaptor assembly that translates power from the handle assembly 12 to the reload and anvil assemblies 16, 18, it is envisioned that the present disclosure could also be incorporated into a manually powered stapling device. Examples of electrically powered stapling devices can be found in U.S. Pat. No. 9,023,014 (“the '014 patent”), and U.S. Pat. No. 9,055,943 (“the '943 patent) which are incorporated herein by reference in their entirety. Alternately, the surgical stapling device 10 can be configured for use with a robotic system and need not include a handle assembly.

Referring to FIGS. 2-3, the reload assembly 16 includes a housing 26, a pusher assembly 28, a knife carrier 30, an annular knife 32 supported on the knife carrier 30, a staple cartridge 34, and staples 36 supported within the staple cartridge 34. The staple cartridge 34 is annular and defines annular rows of staple pockets 40 (FIG. 3). Each of the staple pockets 40 supports one of the staples 36. The pusher assembly 28 includes an annular pusher 42 and a staple pushing member 44 that together define a longitudinal through bore 28 a. The pusher 42 has a distal portion that abuts a proximal portion of the staple pushing member 44 such that distal movement of the pusher 42 within the housing 26 effects distal movement of the staple pushing member 44 within the housing 26. The staple pushing member 44 of the reload 16 has a plurality of fingers 46. Each of the plurality of fingers 46 is received within a respective one of the staple pockets 40 of the staple cartridge 34 and is movable through the respective staple pocket 40 to eject the staple 36 from the staple pocket 40 when the staple pushing member 44 is moved distally within the housing 26 from a retracted position to an advanced position.

Referring also to FIG. 4, the pusher 42 of the pusher assembly 28 includes an inner surface 42 a that defines a portion of the longitudinal through bore 28 a. The inner surface 42 a of the pusher 42 is stepped outwardly at its proximal portion to further define counter bore 43 which is discussed in further detail below.

Referring again to FIG. 3, the anvil assembly 18 includes an anvil shaft 18 a that is releasably coupled to an approximation mechanism (not shown) of the surgical stapling device 10 as is known in the art. The anvil shaft 18 a is movable within a through bore 41 (FIG. 6) defined by an inner housing portion 26 a of the housing 26 as the anvil assembly 18 moves between the spaced and approximated positions in relation to the staple cartridge 34.

Referring to FIGS. 3 and 4A, the knife carrier 30 is movably supported within the through bore 28 a of the pusher assembly 28 between retracted and advanced positions. In the advanced position of the knife carrier 30 (FIG. 7), the knife 30 extends from a distal end of the staple cartridge 32 and in the retracted position of the knife carrier 30 (FIG. 6), the knife 32 is recessed within the staple cartridge 34 to shield the knife 32 from contact by a clinician. The knife carrier 30 includes a substantially cylindrical distal portion 50 and a substantially cylindrical smaller diameter proximal portion 52. The smaller diameter proximal portion 52 is defined by a plurality of spaced resilient legs 53 that define slots 54 there between. The slots 54 receive projections (not shown) defined within the pusher 42 to guide movement of the knife carrier 30 from the retracted position to the advanced position within the pusher assembly 28. The longitudinal slots 54 also facilitate inward flexing of the resilient legs 53 of the knife carrier 30 from a first position in which the resilient legs 53 are engaged with a knife carrier pusher 70 (FIG. 5) (described in detail below) and a second position in which the knife carrier 30 is disengaged from the knife carrier pusher 70 (FIG. 8) as discussed in further detail below. In embodiments, the knife 32 is secured about the distal portion 50 of the knife carrier 30 such as by crimping. Alternately, other fastening techniques can be used to secure the knife 32 to the knife carrier 30. A distal-most portion 50 a of the distal portion 50 of the knife carrier 30 can be recessed to receive the annular knife 32 such that the knife 32 and the knife carrier 30 define a smooth external surface.

Each of the resilient legs 53 of the knife carrier 30 supports an outwardly extending detent 55. The detents 55 can be integrally formed with the respective legs 53 or, alternatively, can be formed as a separate plug 55 a (FIG. 6B) that is inserted into an opening 57 formed in a respective resilient leg 53. The detents 55 are positioned within the counter bore 43 (FIG. 6) of the pusher assembly 28 when the surgical stapling device 10 is in a pre-fired state with the knife carrier 30 and the pusher assembly 28 in retracted positions. Referring also to FIG. 4A, each of the resilient legs 53 of the knife carrier 30 defines a longitudinal axis and includes first engagement structure 60 that is configured to engage a distal portion of the knife carrier pusher 70 of the elongate body 14 as described in detail below to releasably couple the knife carrier 30 to the knife carrier pusher 70 (FIG. 5). In embodiments, the first engagement structure 60 includes an annular channel or recess 60 a that is configured to receive second engagement structure 80 (FIG. 5) formed on a distal portion of the knife carrier pusher 70 as described in further detail below. Although shown as annular, other recess configurations are envisioned. The annular channel 60 a of the first engagement structure 60 is defined by distal and proximal walls, wherein the proximal wall 80 a is substantially orthogonal in relation to the longitudinal axis of the knife carrier 30. In embodiments, a proximal portion 53 a of each resilient leg 53 of the knife carrier 30 is tapered inwardly towards the longitudinal axis of the knife carrier 30 in a proximal direction. The tapered proximal portion 53 a and the longitudinal slots 54 of the knife carrier 30 facilitate attachment of the knife carrier 30 to the distal portion of the knife carrier pusher 70 as the reload assembly 16 is being attached to the elongate body 14 as described in detail below.

Referring also to FIG. 5, the knife carrier pusher 70 includes a substantially cylindrical body 74 having a cutout 75 that extends from a central portion of the body 74 to the distal portion of the body 74. The knife carrier pusher 70 is tubular and includes an inner wall 81 defining a through bore 74 a. In embodiments, the second engagement structure 80 includes a protrusion 81 a formed on a distal portion of the inner wall 81 of the knife carrier pusher 70. Although the protrusion 81 a is shown as being annular, other configurations are envisioned. The annular protrusion 81 a includes a proximal surface 81 b that is substantially orthogonal to a longitudinal axis of the knife carrier pusher 70. The annular protrusion 81 a is received within the annular channel 60 a (FIG. 4A) of the knife carrier 30 when the resilient legs 53 are in the first position (FIG. 6) to couple the knife carrier 30 to the knife carrier pusher 70. The proximal wall 81 b of the annular protrusion 81 a is positioned to engage the proximal wall 80 a (FIG. 6A) defining the annular channel 60 a such that retraction of the knife carrier pusher 70 effects retraction of the knife carrier 30. In embodiments, the cylindrical body 74 of the knife carrier pusher 70 defines recesses 84 that are configured to engage a drive member (not shown) supported within the elongate body 14. The drive member is secured to the proximal portion of the knife carrier pusher 70 and is operable to advance and retract the knife carrier pusher 70 within the housing 26 of the reload assembly 16 as known in the art. U.S. Publication No. 2016/0106406 (“the '406 Publication”) which was filed on Oct. 6, 2015 discloses such an elongate body or adaptor and is incorporated herein in its entirety by reference.

Referring to FIGS. 3 and 5A, the elongate body 14 includes a pusher drive member 90 defining a longitudinal axis and having a tubular body 90 a having an inner surface 92 defining a through bore 92 a. A distal portion of the inner surface 92 defines a leading edge 94 that is tapered outwardly in a distal direction. The through bore 92 a receives the knife carrier 30 and the knife carrier pusher 70 as the knife carrier 30 and the knife carrier pusher 70 are moved between retracted and advanced positions as described in further detail below. The tubular body 90 a includes a proximal portion that is configured to engage structure within the elongate body 14 to effect translation of the pusher drive member 90 between the advanced and retracted positions. The '406 Publication which is incorporated herein in its entirety by reference discloses an elongate body including such structure.

FIGS. 6 and 6A illustrate a distal portion of the stapling device 10 in a pre-fired state. In the pre-fired state, the pusher assembly 28 and the knife carrier 30 of the reload 16 and the knife carrier pusher 70 and the pusher drive member 90 of the elongate body 14 are in retracted positions. In their retracted positions, the pusher assembly 28 and the pusher drive member 90 extend about an interface 106 between the first engagement structure 60 on the proximal portion of the resilient legs 53 of the knife carrier 30 and the second engagement structure 80 positioned on the distal portion the knife carrier pusher 70. In addition, the resilient legs 53 of the knife carrier 30 are in their first position with the detents 55 received within the counter bore 43 of the pusher 42 of the pusher assembly 28, and the knife carrier 30 and the knife carrier pusher 70 are in an engaged state.

FIG. 6B illustrates the distal portion of the surgical stapling device 10 in a post-fired state with the pusher assembly 28 and the pusher drive member 90 moved in the direction indicated by arrows “A” to their advanced positions to eject the staples 36 (FIG. 6) from the staple cartridge 34. In addition, the knife carrier 30, the knife 32, and the knife carrier pusher 70 remain in their retracted positions. In this state, the detents 55 are positioned in a proximal portion of the counter bore 43 such that the resilient legs 53 of the knife carrier 30 remain in their first position and the knife carrier 30 remains in engagement with the knife carrier pusher 70.

FIG. 7 illustrates the distal portion of the surgical stapling device 10 in a post-fired state after the knife carrier pusher 70 and the knife 32 have been moved to their advanced positions in the direction indicated by arrows “B”. In this state, the pusher assembly 28, pusher drive member 90, knife carrier 30 and knife carrier pusher 70 are in their advanced positions with the detents 55 in a central portion of the counter bore 43. As such, the resilient legs 53 of the knife carrier 30 remain in their first position with the first and second engagement structures 60, 80 of the knife carrier 30 and the knife carrier pusher 70 in engagement such that the knife carrier 30 remains coupled to the knife carrier pusher 70.

Referring to FIG. 8, after the staples 36 (FIG. 3) have been fired and tissue has been cut, the pusher drive member 90 is retracted. As discussed above, the pusher drive member 90 is in abutting relation with the pusher assembly 28 and thus, the pusher assembly 28 does not retract with the pusher drive member 90. Subsequently (or simultaneously), the knife carrier pusher 70 is moved to a fully retracted position to retract the knife carrier 30 within the pusher assembly 28 and the pusher drive member 90. As the knife carrier pusher 70 is moved to the fully retracted position, the proximal wall 81 b of the annular protrusion 81 a of the second engagement structure 80 engages the proximal wall 80 a defining the annular channel 60 a such that retraction of the knife carrier pusher 70 effects retraction of the knife carrier 30. Because the walls 80 a and 81 b are substantially orthogonal to the longitudinal axis of the knife carrier 30 as discussed above, the force applied by the wall 81 b onto the wall 80 a does not urge the resilient legs 53 towards their second position.

As the knife carrier 30 is moved towards its retracted position, the detents 55 move through the counter bore 43 such that the resilient legs 53 remain in their first position engaged with the knife carrier pusher 70 to retract the knife 32 into the housing 26 of the reload assembly 16. After the knife 32 is retracted into the housing 26, the detents 55 are positioned to engage the tapered leading edge 94 of the pusher drive member 90. When the detents 55 engage the tapered leading edge 94 of the pusher drive member 90, the resilient legs 53 are urged inwardly in the direction indicated by arrows “C” from their first position towards their second position to disengage the first engagement structure 60 from the second engagement structure 80 and uncouple the knife carrier 30 from the knife carrier pusher 70. By providing detents 55, the present reload assembly 16 does not rely on a back angle on the knife carrier pusher 70 to effect uncoupling of the knife carrier 30 from the knife carrier pusher 70. The detents 55 function to accurately control the timing of separation between the knife carrier 30 and the knife carrier pusher 70 and minimize the likelihood of premature separation of the knife carrier 30 from the knife carrier pusher 70 while minimizing the force required to effect separation of the knife carrier 30 and the knife carrier pusher 70.

As discussed above, the proximal portion 53 a of each resilient leg 53 of the knife carrier 30 is tapered inwardly towards the longitudinal axis of the knife carrier 30 in a proximal direction. Referring again to FIG. 6A, when the reload assembly 16 is attached to the distal portion of the elongate body 14 of the surgical stapling device 10, the tapered proximal portion 53 a of the resilient legs 53 will engage a distal face 100 of the knife carrier pusher 70. Engagement between the tapered proximal portion 53 a of the resilient legs 53 and the distal face 100 of the knife carrier pusher 70 will cam the resilient legs 53 downwardly to allow the first engagement structure 60 to pass by the second engagement structure 80. Due to the resilient nature of the legs 53, the second engagement structure 80 will snap into the first engagement structure 60 when the structures are aligned to couple the knife carrier 30 and the knife carrier pusher 70.

Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the present disclosure. For example, any of the embodiments disclosed herein could include staples with different sizes and/or surfaces with different heights on the staple cartridge and/or anvil. Any of the embodiments disclosed herein can include a surgical buttress that may or may not be used to deliver a therapeutic substance such as a drug or brachytherapy seed. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. 

1. (canceled)
 2. A reload assembly comprising: a housing having a proximal portion and a distal portion; a staple cartridge supported on the distal portion of the housing; a plurality of staples supported in the staple cartridge; a pusher assembly including an annular pusher having an inner surface defining a longitudinal through bore, the inner surface having a proximal portion defining a counter bore, the annular pusher movable within the housing between retracted and advanced positions; a knife carrier movable within the longitudinal through bore of the annular pusher between retracted and advanced positions, the knife carrier having a distal portion and a proximal portion, the proximal portion of the knife carrier defined by resilient legs that are spaced from each other, each of the resilient legs including an outwardly extending detent and first engagement structure, each of the outwardly extending detents received within the counter bore of the annular pusher and being engageable to urge the respective resilient leg inwardly to move the first engagement structure inwardly from an engaged position to a disengaged position; and a knife supported on the distal portion of the knife carrier.
 3. The reload assembly of claim 2, wherein each of the outwardly extending detents is integrally formed with a respective one of the resilient legs.
 4. The reload assembly of claim 2, wherein the first engagement structure includes a recess formed on the proximal portion of each of the resilient legs.
 5. The reload assembly of claim 2, wherein the proximal portion of each of the resilient legs is tapered towards a longitudinal axis of the knife carrier in the proximal direction.
 6. The reload assembly of claim 4, wherein the recess of the first engagement structure is defined by a proximal wall that is orthogonal in relation to a longitudinal axis of the knife carrier.
 7. The reload assembly of claim 2, wherein the reload assembly is adapted to be releasably coupled to a surgical stapling device.
 8. The reload assembly of claim 2, wherein the pusher assembly includes the annular pusher and a staple pushing member having a proximal portion, the staple pushing member engaging the plurality of staples.
 9. The reload assembly of claim 8, wherein the annular pusher is positioned to abut the proximal portion of the staple pushing member.
 10. A surgical stapling device comprising: an elongate body defining a longitudinal axis and having a proximal portion and a distal portion, the elongate body including a pusher assembly drive member and a knife carrier pusher, the pusher assembly drive member having an inner surface defining a through bore and a tapered distal portion; a reload assembly including: a housing having a proximal portion and a distal portion; a staple cartridge supported on the distal portion of the housing; a plurality of staples supported in the staple cartridge; a pusher assembly including an annular pusher having an inner surface defining a longitudinal through bore, the inner surface having a proximal portion defining a counter bore, the annular pusher movable within the housing between retracted and advanced positions; a knife carrier movable within the longitudinal through bore of the annular pusher between retracted and advanced positions, the knife carrier having a distal portion and a proximal portion, the proximal portion of the knife carrier defined by resilient legs that are spaced from each other, each of the resilient legs including an outwardly extending detent and first engagement structure, each of the outwardly extending detents received within the counter bore of the annular pusher and being engageable to urge the respective resilient leg inwardly to move the first engagement structure inwardly from an engaged position to a disengaged position; and a knife supported on the distal portion of the knife carrier; the knife carrier pusher including second engagement structure configured to releasably engage the first engagement structure of the knife carrier to couple the knife carrier pusher to the knife carrier, the first engagement structure being movable from the engaged position engaged with the second engagement structure to the disengaged positioned is engaged from the second engagement structure; wherein when the surgical stapling device is in a pre-fired state, the outwardly extending detents are positioned within the counter bore of the pusher assembly, and when the knife carrier is retracted after the surgical stapling device has been actuated to eject the plurality of staples and to dissect tissue, the outwardly extending detents are positioned to engage the tapered distal portion of the pusher assembly drive member to urge the first engagement structure from the engaged position towards the disengaged position to uncouple the knife carrier from the knife carrier pusher.
 11. The surgical stapling device of claim 10, wherein each of the outwardly extending detents is integrally formed with a respective one of the resilient legs.
 12. The surgical stapling device of claim 10, wherein the first engagement structure includes a recess formed on the proximal portion of each of the resilient legs.
 13. The surgical stapling device of claim 10, wherein the proximal portion of each of the resilient legs is tapered towards a longitudinal axis of the knife carrier in the proximal direction.
 14. The surgical stapling device of claim 12, wherein the recess of the first engagement structure is defined by a proximal wall that is orthogonal in relation to a longitudinal axis of the knife carrier.
 15. The surgical stapling device of claim 10, wherein the reload assembly is releasably coupled to the elongate body.
 16. The surgical stapling device of claim 10, wherein the pusher assembly includes the annular pusher and a staple pushing member having a proximal portion, the staple pushing member engaging the plurality of staples.
 17. The surgical stapling device of claim 10, wherein the annular pusher is positioned to abut the proximal portion of the staple pushing member. 